Toner for electrophotography

ABSTRACT

A toner for electrophotography containing a compound represented by the following formula (1) ##STR1## wherein R represents an alkyl group, --A-- represents --O--COCH═CH-- or --S--CH 2  CH 2  -- and L is an integer of 2 to 10. 
     The toner for electrophotography has a sharp distribution for the charging amount, excellent moisture resistance and stability to aging. As a result, the toner can provide an image of extremely high gradation and shows satisfactory performance of replicate image formation.

DESCRIPTION

1. Technical Field

The present invention concerns a toner. More specifically, it relates toa toner for developing electrostatic latent images forelectrophotography, electrostatic recording, etc.

2. Background Art

A process for forming an image of electrostatic recording,electrophotography, etc. by utilizing static electricity comprises astep of forming a photoconductive latent image by an optical signal onphotosensitive material obtained by coating photoconductive materialsuch as selenium, cadmium sulfide or amorphous silicon on a substratemade of aluminum, paper, etc., and a step of electrically chargingcolored fine particles of 5-50 μm referred to as a toner frictionally bymeans carrier (iron powder, ferrite powder, etc.) in two componentdevelopment or directly in mono component development and then actingthem on a photoconductive latent image thereby developing the same.

It is necessary that the toner is applied with electric chargecorresponding to the polarity of a photoconductive latent image formedon the photosensitive material, that is, either positive or negativecharge.

Generally, fine colored particles referred to as a toner comprises abinder resin and a coloring agent as the essential ingredient and,optionally, a magnetic powder, etc. As a method of applying electriccharge to a toner, it is possible to utilize charging property of abinder resin itself without using a charge control agent, but stabilityto aging and moisture resistance is usually poor and no satisfactoryimage quality can be obtained by this method. Accordingly, a chargecontrol agent is usually added with an aim of retaining and controllingcharges of a toner. The properties required as the quality of a tonerincludes excellent charging property, flowing property and fixingproperty, and they are greatly influenced by the charge control agentused for a toner.

As the charge control agent added to a toner, there have been known, (1)colored negative charge control agents such as 2:1 metal complex saltdye (Japanese Patent Publications No. 45-26478 and No. 41-201531) andphthalocyanine pigment (Japanese Patent Application Laid Open (KOKAI)No. 52-45931), and colorless negative charge control agents as describedin Japanese Patent Publication No. 59-7384 or Japanese PatentApplication Laid Open No. 61-3149, (2) positive charge control agentssuch as nigrosine dyes, various kinds of quaternary ammonium salts(Journal of Electrostatic Society, 1980, Vol.4, No. 3, P-114). However,a toner containing these charge control agents can not satisfy theproperty required for the quality of the toner such as charging propertyand stability to aging. For instance, a toner containing 2:1 metalcomplex salt dye known as a negative charge control agent has a certainlevel of charging amount but involves a drawback that the dispersibilityof the 2:1 metal complex salt dye to a binder resin is generally poor.Therefore, it does not distribute uniformly in binder resin, and thedistribution for the charging amount of the resultant toner remarkablylacks in the sharpness. The resultant image obtained by using such atoner has low gradation and poor image forming performance. In addition,since the 2:1 metal complex salt dye has a hue near black color, it hasa drawback that it can be used only for a toner of a restricted huebased on black color. As a nearly colorless negative charge controlagent, there can be mentioned a metal complex of an aromaticdicarboxylic acid (Japanese Patent Publication No. 59-7384), but thishas a drawback that it can not be completely colorless anddispersibility is not satisfactory. Further, as a colorless negativecharge control agent, there has been known a compound proposed byJapanese Patent Application Laid Open (KOKAI) No. 61-3149, but thecompound, having a low melting point, involves a drawback that the heatstability upon toner production is poor and production of stable toneris difficult. Accordingly, it has been demanded for the development of atoner in which the charge control agent is well dispersed to a binderresin and uniformly distributed in a toner to provide an image of highgradation.

DISCLOSURE OF INVENTION

The present inventors have made an earnest study for solving theforegoing problems and, as a result, have accomplished the presentinvention based on the finding that the distribution of the chargingamount of the toner is sharp and the charging property is remarkablyimproved by incorporating the compound of the following formula (1) intoa toner. ##STR2## wherein R represents alkyl group, --A-- represents--O--COCH═CH-- or --S--CH₂ CH₂ -- and L is an integer of 2 to 10.

The compound of the formula (1) functions as a negative charge controlagent which has a satisfactory compatibility with a binder resin and atoner incorporated with the compound shows high specific charging amountand satisfactory stability to aging and, accordingly, can provide stableand clear image upon forming an image in electrostatic recording even ifa toner is stored on a long period of time.

As preferred examples of the compound of the formula (1) incorporated asa charge control agent into a toner in the present invention there canbe mentioned the following compounds:

Specific examples of compound

As the compounds represented by the following formula (2): ##STR3##wherein R and L have the same meanings as described above, there can bementioned the followings. ##STR4##

Each of the compounds (3), (4) and (5) is a mixture of compounds inwhich L is 2 to 10.

These compounds can be synthesized by a known methods, for example, byacting maleic acid to an organic tin oxide. Further, a compoundbelonging to the following formula (6) can also be mentioned as apreferred example. ##STR5## wherein R and L have the same meanings asdescribed above. ##STR6##

Each of the compounds (7), (8) and (9) is a mixture of compounds inwhich L is 2 to 10. These compounds can be synthesized by known methods,for example, by acting a corresponding carboxylic acid, maleic acidanhydride and a corresponding alcohol to an organic tin sulfide.

BEST MODE FOR CARRYING OUT THE INVENTION

For producing a toner containing the compound of the formula (1)described above, there is a method of kneading a mixture comprising thecompound of the formula (1), a coloring agent and a binder resin in adevice capable of mixing under heating such as a heating kneader or twinroll, under the molten state of the binder resin, which is then cooledto solidify and pulverized by a pulverizer such as a jet mill or ballmill into 1 to 30 μm (particle size), or a method of dissolving acoloring agent, a binder resin and the compound of the formula (1)together into a solvent (for example, acetone or ethylacetate), applyingagitation, then pouring into water for reprecipitation, filtering,drying and then pulverizing by a pulverizer such as a ball mill into 1to 30 μm (particle size).

The binder resin is used usually by 8.9 to 65%, more preferably, 98 to85%, the coloring agent is used by 1.0 to 15%, more preferably, 1.5 to10% and the charge control agent is used by 0.1 to 30%, more preferably,0.5 to 5% (each in weight ratio) in this case.

The coloring agent for use with the toner for electrophotographaccording to the present invention (abbreviations shown hereinafterrepresent the following meanings: CI: Color Index, Pig: Pigment, Dis:disperse, Sol: solvent, Y: yellow, R: red and B: blue) can include thoseknown coloring agents such as inorganic pigment, for example, carbonblack and ultramarine;.organic pigments, for example, CI-Pig-Y-1,CI-Pig-R-9, CI-Pig-B15, etc.; oil soluble dyes such as CI-Sol-Y-93,CI-Sol-R-146, CI-Sol-B-35, CI-Dis-Y-42, CI-Dis-R-59, CI-Sol-B-81, etc.As the binder resin, these can be used polystyrene, styrene-acrylic acidcopolymer, styrene propylene copolymer, styrene acrylonitrile copolymer,acryl resin, styrene-maleic acid copolymer, polyvinyl chloride,polyvinyl acetate, olefin resin, polyester resin, polyurethane resin andepoxy resin, either along or a mixture.

In addition, into the toner for electrophotography according to thepresent invention, there may be added, as required, a flowing agent suchas silicon oxide, antifoggant such as mineral oil, various kinds ofmagnetic substance used for monocomponent development, electrifyingagent such as zinc oxide, anti set agent such as low molecular weightpolyethylene and low molecular weight polypropylene.

The toner obtained in the present invention is formulated into adeveloper, for example, by mixing with an iron powder (carrier) of about200 mesh at a weight ratio, for example, of 2 to 8: 98 to 92 (toner:iron powder) and used for the developing step in electrophotography.

The toner for electrophotography according to the present invention hassharp charging amount distribution and satisfactory stability to agingas compared with toners using conventional charge control agent. As aresult, it has a feature capable of obtaining an image of extremely highgradation, while showing excellent performance of replicate imageformation.

EXAMPLE

The present invention is to be explained more specifically by way ofexamples. In the examples, "parts" means "parts by weight" unlessotherwise specified.

Example 1

    ______________________________________                                        Styrene-butyl acrylate copolymer (binder)                                                                100 parts                                          Low molecular weight polyethylene                                                                        2 parts                                            CI-Dis-Y-164 (coloring agent)                                                                            1.2 parts                                          Compound of Formula (3) (mixture of L = 2-10)                                                            1.5 parts                                          ______________________________________                                    

The above mentioned composition was melt kneaded by a kneader adjustedto 140° C. for 10 min and then cooled to solidify. Then, after coarselypulverizing by a coarse pulverizer, it was finely pulverized by a jetmill pulverizer and then classified in an air stream classifier toobtain a toner of 8 to 20 μm particle size.

The resultant toner was mixed with iron powder carrier of about 200 meshat a weight ratio of 3:97 (toner:iron powder carrier) to obtain adeveloper A. Then, when the initial specific charging amount of thedeveloper A was measured by a blow off charge amount measuring device,it was -23.4 μc/g. When copying was conducted in a copying machine usingthe developer A, a clear yellow image excellent in gradation and notdeteriorating the hue inherent to the coloring agent was obtained.Further, when a test for stability to aging was conducted by using thedeveloper A (test for the change of the charging amount with time andtest for moisture resistance and stability to aging), the results shownin the following Table 1 were obtained.

                                      TABLE 1                                     __________________________________________________________________________                             Test for moisture re-                                                         sistance with time                                          Test for change of charging amount                                                              (-μc/g)                                                  with time (-μc/g) (hour)                                                                         After                                                                             Decreasing                                          1  2  3  4  5  6  Initial                                                                           1 week                                                                            rate (%)                                     __________________________________________________________________________    Developer A                                                                          23.6                                                                             23.8                                                                             23.5                                                                             23.3                                                                             23.1                                                                             23.0                                                                             23.4                                                                              23.1                                                                              1.3                                          __________________________________________________________________________

As can be seen from the results above, the stability of the developer Ato aging was excellent.

Stability test to aging Test, for the change of charging amount withtime

The developer A (mixture of toner and iron power carrier) was weighed ina plastic vessel, applied with ball milling at 100 rpm, to measure thecharging amount of the toner on every hours (1 to 6 hr).

Test for moisture resistance with time

After charging for one hour in a plastic vessel according to the abovementioned method "test for the change of charging amount with time", thedeveloper was left for one week in an 10% moisture atmosphere (at roomtemperature) with the vessel open to measure the charging amount of thetoner.

EXAMPLE 2

A developer B was obtained in the same procedures as in Example 1 exceptfor using 2.0 parts of the compound of the formula (7) (mixture of L =2to 10) instead of the compound of the formula (3) in Example 1. Theinitial specific charging amount of the developer B was -21.4 μc/g. Whenthe stability test to aging was conducted, the results were obtained asshown in the following Table 2.

                                      TABLE 2                                     __________________________________________________________________________                             Test for moisture re-                                       Test for change of charging amount                                                              sistance with time                                          with time (-μc/g) (hour)                                                                     (-μc/g)                                                  h: hour               After                                                                             Decreasing                                          1 h                                                                              2 h                                                                              3 h                                                                              4 h                                                                              5 h                                                                              6 h                                                                              Initial                                                                           1 week                                                                            rate (%)                                     __________________________________________________________________________    Developer B                                                                          21.6                                                                             21.8                                                                             21.5                                                                             21.3                                                                             21.1                                                                             21.0                                                                             21.4                                                                              21.1                                                                              1.4                                          __________________________________________________________________________

As apparent from the foregoing results, the stability of the developer Bto aging was excellent.

EXAMPLE 3

    ______________________________________                                        Polyester resin (binder)                                                                              100 parts                                             Carbon black (coloring agent)                                                                         6.0 parts                                             Compound of formula (4) 2.0 parts                                             (mixture of L = 2 to 10)                                                      ______________________________________                                    

The mixture of the above mentioned composition was melt kneaded by akneader adjusted to 160° C. for 10 min and then cooled to solidify.Then, after coarsely pulverizing by a coarse pulverizer, it was finelypulverized by a jet mill pulverizer and then classified in an air streamclassifier to obtain a toner of 8 to 20 μm particle size.

The resultant toner was mixed with an iron powder carrier of about 200mesh at a weight ratio of 3:97 (toner:iron powder carrier) to obtain adeveloper C. Then, when the initial specific charging amount of thedeveloper C was measured by a blow off charge amount measuring device,it was -21.3 μc/g. When copying was conducted in a copying machine usingthe developer C, a clear black image of excellent gradation wasobtained.

When the same stability test to aging as in Example 1 was conducted byusing the developer C, the results as shown in the following Table 3were obtained.

                                      TABLE 3                                     __________________________________________________________________________                             Test for moisture re-                                       Test for change of charging amount                                                              sistance with time                                          with time (-μc/g) (hour)                                                                     (-μc/g)                                                  h: hour               After                                                                             Decreasing                                          1 h                                                                              2 h                                                                              3 h                                                                              4 h                                                                              5 h                                                                              6 h                                                                              Initial                                                                           1 week                                                                            rate (%)                                     __________________________________________________________________________    Developer C                                                                          21.5                                                                             21.6                                                                             21.4                                                                             21.3                                                                             21.2                                                                             21.0                                                                             21.6                                                                              21.3                                                                              1.4                                          __________________________________________________________________________

As apparent from the results, the stability of the developer C to agingwas excellent.

EXAMPLE 4

A developer D was obtained in the same procedures as in Example 3 exceptfor using 1.5 parts of the compound of the formula (8) (mixture of L =2to 10) instead of the compound of the formula (4) in Example 3. Theinitial specific charging amount of the developer D was -19.8 μc/g. Whenthe stability test to aging was conducted, the results as shown in thefollowing Table 4 were obtained.

                                      TABLE 4                                     __________________________________________________________________________                             Test for moisture re-                                       Test for change of charging amount                                                              sistance with time                                          with time (-μc/g) (hour)                                                                     (-μc/g)                                                  h: hour               After                                                                             Decreasing                                          1 h                                                                              2 h                                                                              3 h                                                                              4 h                                                                              5 h                                                                              6 h                                                                              Initial                                                                           1 week                                                                            rate (%)                                     __________________________________________________________________________    Developer D                                                                          19.7                                                                             19.9                                                                             19.7                                                                             19.5                                                                             19.4                                                                             19.2                                                                             19.6                                                                              19.3                                                                              1.5                                          __________________________________________________________________________

As apparent from the foregoing results, the stability of the developer Dto aging was excellent.

EXAMPLE 5

    ______________________________________                                        Styrene-methyl acrylate copolymer (binder)                                                              100 parts                                           Low molecular weight polypropylene                                                                      3 parts                                             CI Sol-Blue-111 (coloring agent)                                                                        1.5 parts                                           Compound of formula (5)   2.5 parts                                           (mixture of L = 2 to 10)                                                      ______________________________________                                    

The mixture described above was dissolved into 1000 parts of a mixedsolvent of acetone and ethyl acetate (1:1.volume ratio) and then stirredat ordinary temperature for 1 hour. Then, the mixed solution was droppedinto 10000 parts of water under stirring to reprecipitate. By filteringand drying the resultant crystals, toner of coarse particles wereobtained. Then, they were finely pulverized by a jet mill pulverizerand, further, classified by an air stream classifier to obtain toners of8 to 20 μm particle size.

The resultant toner was mixed with an iron powder carrier of about 200mesh at a weight ratio of 3:97 (toner:iron powder carrier) to obtain adeveloper E. Then, when the initial specific charging amount of thedeveloper E was measured by a blow off charge amount measuring device,it was -23.3 μc/g. When copying was conducted in a copying machine usingthe developer E, a clear blue image of excellent gradation and notdeteriorating the hue inherent to the coloring agent was obtained.

When the same stability test to aging as in Example 1 was conducted byusing the developer E, the results as shown in the following Table 5were obtained.

                                      TABLE 5                                     __________________________________________________________________________                             Test for moisture re-                                       Test for change of charging amount                                                              sistance with time                                          with time (-μc/g) (hour)                                                                     (-μc/g)                                                  h: hour               After                                                                             Decreasing                                          1 h                                                                              2 h                                                                              3 h                                                                              4 h                                                                              5 h                                                                              6 h                                                                              Initial                                                                           1 week                                                                            rate (%)                                     __________________________________________________________________________    Developer E                                                                          23.2                                                                             23.4                                                                             23.1                                                                             22.9                                                                             22.7                                                                             22.6                                                                             23.1                                                                              22.7                                                                              1.7                                          __________________________________________________________________________

As shown in the results above, the stability of the developer E to agingwas excellent.

EXAMPLE 6

A developer F was obtained in the same procedures as in Example 5 exceptfor using 1.5 parts of the compound of the formula (9) (mixture of L=2to 10) instead of the compound of the formula (5) in Example 5. Theinitial specific charging amount of the developer F was -22.1 μc/g. Whenthe stability test to aging was conducted, the results as shown in thefollowing Table 6 were obtained.

                                      TABLE 6                                     __________________________________________________________________________                             Test for moisture re-                                       Test for change of charging amount                                                              sistance with time                                          with time (-μc/g) (hour)                                                                     (-μc/g)                                                  h: hour               After                                                                             Decreasing                                          1 h                                                                              2 h                                                                              3 h                                                                              4 h                                                                              5 h                                                                              6 h                                                                              Initial                                                                           1 week                                                                            rate (%)                                     __________________________________________________________________________    Developer F                                                                          22.2                                                                             22.4                                                                             22.1                                                                             21.7                                                                             21.4                                                                             21.3                                                                             22.1                                                                              21.7                                                                              1.8                                          __________________________________________________________________________

As apparent from the results above, the stability of the developer F toaging was excellent.

INDUSTRIAL APPLICABILITY

The toner for electrophotography obtained in the present invention hassharp charge amount distribution excellent moisture resistance andstability to aging. As a result, the toner can provide an image of highgradation and show satisfactory performance of replicate imageformation. Further, since the charge control agent itself used in thetoner according to the present invention is substantially colorless, itis possible to select to coloring agent in line with the hue requiredfor the color toner and the hue inherent to the dye or pigment is notdeteriorated at all and, accordingly,, it has excellent industrialapplicability as the toner in electrophotography and electrostaticrecording.

We claim:
 1. A toner for electrophotography containing a compoundrepresented by the following formula (1) ##STR7## wherein R representsan alkyl group, --A-- represents --O--COCH═CH-- or --S--CH₂ CH₂ -- and Lis an integer of 2 to
 10. 2. A toner for electrophotography according toclaim 1, wherein the compound represented by the formula (1) is acompound represented by the following formula: ##STR8## wherein R and Lin the formula (2) have the same meanings as described above.
 3. A tonerfor electrophotography according to claim 2, wherein the compoundrepresented by the formula (2) is a compound represented by thefollowing formula: ##STR9## wherein L in the formula (3) has the samemeanings as described above.
 4. A toner for electrophotography accordingto claim 2, wherein the compound represented by the formula (2) is acompound represented by the following formula: ##STR10## wherein L inthe formula (4) has the same meanings as described above.
 5. A toner forelectrophotography according to claim 2, wherein the compoundrepresented by the formula (2) is a compound represented by thefollowing formula: ##STR11## wherein L in the formula (5) has the samemeanings as described above.
 6. A toner for electrophotography accordingto claim 1, wherein the compound represented by the formula (1) is acompound represented by the following formula: ##STR12## wherein R and Lin the formula (6) have the same meanings as described above.
 7. A tonerfor electrophotography according to claim 6, wherein the compoundrepresented by the formula (6) is a compound represented by thefollowing formula: ##STR13## wherein L in the formula (7) has the samemeanings as described above.
 8. A toner for electrophotography accordingto claim 6, wherein the compound represented by the formula (6) is acompound represented by the following formula: ##STR14## wherein L inthe formula (8) has the same meanings as described above.
 9. A toner forelectrophotography according to claim 6, wherein the compoundrepresented by the formula (6) is a compound represented by thefollowing formula: ##STR15## wherein L in the formula (9) has the samemeanings as described above.